Update EHV-1 in San Mateo County

March 15, 2007

 

Update EHV-1 in San Mateo County

 

The first confirmed cases of the neurotropic (neurological) form on Equine Herpes Virus in San Mateo County were recently identified by Bayhill Equine. Three cases were identified at a boarding facility in Montara, north of Half Moon Bay on March 12. A 4-yr old pleasure horse became febrile on March 6^th. She began showing slight signs of ataxia on the evening of March 11^th, and was unable to stand the next morning.  At that time, one other horse in the paddock was also ataxic.  Based on history, clinical signs, and the number of horses affected.  A presumptive diagnosis of Equine Herpes Virus was made, and the horse referred to the UC-Davis Large Animal Clinic.  The diagnosis was confirmed the afternoon of March 12 based on a positive nasal swab, blood, and spinal tap. Two other horses at the boarding facility have also tested positive, with one other pending.  Two of the affected horses were subsequently euthanized at UC-Davis after failing to respond to treatment. Currently, three stables in the Moss Beach/Montara area are under voluntary quarantine to help stop the spread of the virus.

 

The neurotropic form of EHV-1 was first found in a horse imported from Europe and sent down to Florida for the winter shows in Wellington. A total of 6 horses died or were euthanized in Florida.  One horse that was part of the initial quarantine with the horse from Europe died in Rancho Santa Fe, CA.  Two horses had Los Alamitos Racetrack were euthanized recently.  The three Bay Area racetracks were recently under quarantine when one horse at Golden Gate Fields was diagnosed with the neurotropic form.

 

To date, there is NO vaccine labeled effective against the neurotropic form of EHV-1.  One small study of 5 horses demonstrated that a modified live virus vaccine reduced the amount and duration of shedding of the virus, and horses vaccinated did not exhibit neurologic signs. However, this vaccine has not been challenged against this current viral strain.

 

Treatment is generally supportive with the exception of Valtrex (Valcyclovir). This is an anti-viral drug with is given twice a day for 7 days.  However, it is very expensive, with a cost of approximately $2,500 for the course of treatment.

 

Immunomodulators such as Zylexis or EqStim may be beneficial in boosting your horse?s immune system against a viral challenge. Please refer to our previous handouts for additional information on the vaccine, immunodulators, and web sites about this disease.

 

Please feel free to call us with any additional questions.

 

 

The Doctors and Staff of Bayhill Equine, Inc.